1. Field of the Invention
The invention relates to an electrostatic adsorption device.
2. Related Art Statement
A technique of joining an electrostatic chuck onto a metal cooling board of the water cooling type by means of metal bonding was proposed by (Japanese Patent laid-open (Kokai) Publication A3249/1991). According to this technique, an electrostatic chuck with an alumina substrate and a water cooling plate made of aluminum are joined by metal bonding using indium metal.
Alternatively, it has been proposed to produce an electrostatic chuck by forming a metal film on the surface of a ceramic insulating plate and bonding the surface of the plate having the metal film onto the surface of another ceramic supporting substrate using an adhesive (Japanese Patent laid-Open publication A183143/2000). According to this publication, the positive and negative electrodes of an electrostatic chuck of the bipolar type are formed on the ceramic insulating plate. Moreover, it was disclosed to use the electrode for an electrostatic chuck as an electrode for generating plasma at the same time, for example in Japanese Patent Laid-Open publication A17849/1997.
Recently, the density of plasma generated over the adsorption face of an electrostatic chuck has been considerably improved. It is demanded to form a finer electrode pattern embedded within the ceramic substrate of an electrostatic chuck for improving the density of the plasma generated over the electrostatic chuck. When such fine electrode patterns are embedded within the ceramic sintered body, a gap or gaps are formed defined by the electrode pattern. When the electrode pattern is finer, however, it becomes more difficult to secure the insulation in the gap defined by the electrode pattern. The reasons are as follows. When the gap in the electrode pattern is narrow, it is difficult to sufficiently supply ceramic particles into the gap during a sintering process of a ceramic shaped body. Such difficulty of supplying the ceramic particles may result in the incomplete sintering and thus insufficient insulation in the gap defined by the electrode pattern.
An object of the invention is to provide an electrostatic adsorption device having a resistance against a corrosive substance such as plasma.
Another object of the invention is to provide an electrostatic chuck enabling sufficient insulation in the gap defined by the electrode pattern when a finer electrode pattern is formed.
The invention provides an electrostatic adsorption device comprising:
a dielectric layer made of a ceramic dielectric material and having an adsorption face and a back face;
an electrode provided on the back face of the dielectric layer, the electrode defining a gap;
a cooling member; and
an insulating adhesive provided between the back face of the dielectric layer and the cooling member,
wherein the insulating adhesive covers the electrode and the back face and is provided in the gap.
The inventors provided an electrode pattern on the back face of the ceramic dielectric layer and bonded the dielectric layer to the cooling member using an insulating adhesive. In the structure, the adhesive covers the electrode and the back face of the dielectric layer and is filled in the gap defined by the electrode. The insulation in the gap formed by the electrode pattern may be successfully improved even when a finer electrode pattern is provided, while securing the resistance of the device against a corrosive substance by means of the ceramic dielectric layer.
These and other objects, features and advantages of the invention will be appreciated upon reading the following description of the invention when taken in conjunction with the attached drawings, with the understanding that some modifications, variations and changes of the same could be made by the skilled person in the art.